Patent GB-781041-A (GB)
Title: Improvements in or relating to machines for manipulating cut tobacco
IPC: A24C5/34
Filed: 1951-08-15
Abstract: 781,041. Automatic control systems for tobacco machines. POWELL, G. F. W., and MOLINS MACHINE CO., Ltd. Aug. 15, 1952 [Aug. 15, 1951], No. 19270/51. Class 38 (4). In a machine in which feeding means supply cut tobacco to a moving conveyer, an electrical signal produced in dependence on the mass of a length of the tobacco on the conveyer is modified by the addition of its time differential and/or integral and serves to control automatically in a continuous manner the relative speeds of the feeding means and the conveyer. In a cigarette making machine, Fig. 1, tobacco is fed from a hopper 1 on to a travelling endless belt 2 which transfers it on to a paper web 3 supplied from a reel 4 through a printer 5. The loaded web is carried by an endless tape 7 through a wrapper 8, a paster 9 and a heater 10 so that a continuous cigarette rod 51 emerges to be severed by a cutter 11 into cigarettes which pass on to an endless belt 12 from which they are transferred by deflectors 13 on to a catcher band 14. The cigarette rod passes through a Beta-ray mass measuring unit at III, the electrical output of which is representative of the mass of a predetermined length of the rod. In this unit the cigarette rod passes between guides 112, 113, Fig. 6. Radiation from a Beta-ray source 111, after passing through an aperture 135 in a screen 124 and through the cigarette rod, influences an ionization chamber 110 to produce the electrical signal. Ray source 111 is adjustable towards and away from the ionization chamber 110 by means of a knob 159 and a pointer 160 indicates the set position. When checking the measuring unit the cigarette rod is broken and deflected away from guides 112, 113 by a manually positioned plate (not shown). A knob 129 is then operated to move screen 124 so that duralumin diaphragms 125, 126, 127 of thicknesses equivalent to different known masses of tobacco are brought between the ray source and the ionization chamber. If, by releasing a clamp 151 ionization chamber 110 is swung away in the direction of the arrow, the operator is protected by a flap 147 which moves automatically to cover the opening of ray source 111. Heaters 164 prevent condensation within the measuring unit. The mass measuring unit may alternatively be associated with the tobacco on belt 2 at position I, Fig. 1, or with the loaded web on tape 7 at position II. The output of a second identical measuring unit with between its ray source and ionization chamber, a metal diaphragm equivalent to the desired tobacco mass is connected in opposition to the first to produce a signal dependent on the mass error. This second unit may also be associated with the empty tape at position IV to provide compensation for tape wear. Air blowers may remove dust from the measuring units and/or the tape may be automatically scraped clean. The mass error signal is a direct voltage which is converted to alternating voltage by a vibrating electrical condenser the output of which is amplified and rectified to operate (a) a thermionic valve voltmeter indicating the magnitude and sense of mass error, and (b) thermionic valve relays controlling a reversible motor 16, Fig. 1, or solenoid-operated ratchets 45 to adjust, through a shaft 20, an exparding pulley 23 in the drive between a main shaft 21 and the hopper shaft 15 so that the tobacco mass is corrected. Differential and integral components are introduced into the control by resistance-capacity networks. To compensate for variation in moisture content of the tobacco a stream of tobacco of predetermined section is extracted from the hopper on a narrow tape 177, Fig. 16, and passed under a roller 180 on which conducting rings form electrodes between which the conductivity of the tobacco is measured in a bridge circuit the output of which controls, through a thermionic valve relay, an electromagnetically-operated ratchet mechanism adjusting a potentiometer supplying a compensating voltage to the automatic mass control system so that the total mass is increased with increase in moisture and vice versa. The ratchet mechanism also operates a pointer indicating moisture content. Specifications 558,491, 587,210, 684,503, 781,043, [Group XL (b)], and 781,044 are referred to.